A thermoplastic polyurethane resin (TPU) is generally a rubber elastic body obtained by reaction of a polyisocyanate, a high molecular weight polyol, and a low molecular weight polyol, and includes a hard segment formed by reaction of the polyisocyanate and the low molecular weight polyol and a soft segment formed by reaction of the polyisocyanate and the high molecular weight polyol.
It has been known that the thermoplastic polyurethane resin, along with a foaming agent, is melted and molded, so that a foaming molded article is obtained.
To be specific, for example, it has been proposed that a pellet of the thermoplastic polyurethane resin is produced from a 4,4′-diphenylmethane diisocyanate (MDI) as a polyisocyanate, a polyester polyol made of an adipic acid and a 1,4-butanediol as a high molecular weight polyol, and a 1,4-butanediol as a low molecular weight polyol, and the pellet, along with a foaming agent, is melded and molded, so that a foaming molded article is obtained (ref: Patent Document 1).